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MG MGB Technical - MGB Fuel Tank EFI

For some reason I can't find my old post, so I'm re-posting!

Basically I'm fitting EFI to my MGB. Its a 1972 MGB GT and I'm having pure stress with the tank.

I know some tanks have return lines, but don't know which?!? Does mine, is it suitable?!? I need to know what is the best/easiest/cheapest way of making my tank EFI compatible.

Frontline have stopped making their EFI baffled tanks, so that option is out for the time being.

I could get a fuel cell, but that would involve cutting/welding the boot around which I don't really want to do. Ideally I would like one with an internal swirl pot (unlikely).

Anyway, what are your suggestions guys?!? What do you use for your EFI GTs?

Also, what size lines do you guys use, 1/2", 3/8"???


Thanks

Olly
OT Hayter

I don't know of any MGB fuel tanks with built-in
return lines as no MGB had EFI as stock.

I suppose the vent line could be utilized for this
- but then you'd have to somehow vent the tank
in order to account for fuel expansion during temp
changes.

If you're going through all the trouble and hassles
of installing an EFI, then you might consider getting
a new/used tank and having a qualified fuel tank
repair shop braze a return line fitting onto it.

Daniel Wong

No need to braze - all OE fittings are soft soldered in!

UK tanks don't have a vent fitting - but you can buy US/Canadian spec tanks in the UK (I have some) and use the vent.

Easier still, as your tank will have the outlet fitting near the top of the tank is just to change the sender unit for the later one with built in pickup, cut this off short and use it as the return.

You can make up an external swirl pot if you have problems with air bubbles in the fuel.
Chris at Octarine Services

Use the same size lines as the fuel lines on the MGB. The vent lines are smaller.
For ease of installation, get the fuel line from a salvage yard and use it as the return line.
See here for more details on one way to do it:
http://home.comcast.net/~whaussmann/Bosch_MGB/fueldelivery1.htm

Got to 'Back' on the bootom left of the page to see a couple of other MG installs

Werner
werner haussmann

You will not be able to use an MGB tank unless you fit it with a swirl pot. This can be done if you are good at bronzing - just get a swirl pot from another [EFI] tank and bronze it in place.

Or you can fit an external swirl pot.

I bought an EFI tank from Frontline not so long ago and he had others in stock at the time. £200 though.
Hal Adams

Strange, but my Ford 5.0 EFI with 24# injectors work great WITHOUT a swirlpot. i agzonized many hours about the swirlpot situation and finally decided to give my idea a try. BTW, i have a 1978 MGB. removed the sending unit and shortened the pick-up as much as possible;,then i bent it forward to avoid cavitation by the returning fuel. apparently it hit the right front lower part of the tank. this is my return line 5/16" and the existing line was used. then a hole was drilled at the right rear lower corner of the tank for access and pickup. a 3/8" line was used since the MSD brand EFI pump has a 3/8 inlet. a 5/16" ( 5/16 out o the pump) steel line was made and routed to the front for the pressure line. a custom Bung was made by a machinist friend and threaded on the exterrior for 3/8 npt. the bung had a flange larger than the hole to solder to the tank. the 3/8 steel line came from a length of chev. truck in the salvage yard. with the sending unit out, i was able to bend the 3/8"line forward and down so it sat in the original sump in the tank. foutunatly i had a 3/8 screen from another ford truck sending unit & pick-up. with a small Mag-lite, i could illuninate the tank interior and place the line for optimum position. the internal 3/8 line was soldered to the bung (kind of press fit) after i marked the correct position. the external flange was also marked and soldered, then double cked after both operations. my EFI pump was located in the right lower QP area just behind the wheel. a 3/8 plate was welded to the factory tow point on the frame rail and a custom plate was bolted to that. the custom plate is removable so i have a pump module that can be removed as an assembly. the wiring was simple. the white pump wire at the rear was used as a trigger for a relay, with the relay power leg coming from a fused feed direct at the positive battery terminal. this pos. feed travels thru a Ford "upset" or crash sensor that will disconnect power on a heavy impact. Does it work?? yes and works well. the pump is lower than the tank in its location. the line starts low in tank and rises then falls back to a lower level at the pump. once the pump primes, it is gravity flow and works great. after doing the Tail of the Dragon this summer at the V8 conversion meet, i refilled the car it was still running and no sputtering) with 12.6 gallons of fuel. must work ok? Swirlpots and extra cannister fuel filters are ok but apparently not necessary if one approaches this in a thoughtful manner. will gladly share my info if needed. you can check my conversion on the V8 Conversion web-site.
have a great day & Safety Faster
kelly stevenson

A 72 has a tank that has a fuel pipe outlet located towards the back on the right hand side. It points forward. In the middle of the side of the tank you have where the fuel gauge sender and its float attaches. A circle roughly three inches diameter.

This is an off the shelf parts approach.
It works well (about three years so far).
It is easy to set up.

Remove the old fuel float and sender and replace it with one from a very late model MGB. This sender has its own fuel pick up incorporated into it (as well as the float and sender).. My one cost me around $55 Australian .
This gives you a pipe in and a pipe out of the tank with standard off the shelf parts.
If you wanted to save a little money, you could remove the older sender and float to a safe distance from the flammable tank and attach a home made fuel inlet pipe.

You will then need to buy a large EFI fuel filter (around $20 K mart etc), a high pressure fuel pump and also a low pressure feeder pump.
You set this up, with fuel line, in the following sequence.
1-New fuel outlet to filter.
2-Filter to feeder pump.
3-Feeder pump to high pressure pump.
4-High pressure pump to engine.
5-Engine to other/old fuel tank line, back into the tank.

The filter will protect the fuel injection system as well as acting as an antisurge chamber (or swirl pot). This gear may be put in the boot, of you like.

The feeder pump is made by Pierburg in Germany and is called an Auto-suction vane cell pump. stock no. 12001. it can deliver 0.5 bar when used as a primary pump. It cost $95 Australian (apply exchange rate to get an idea what it might cost locally) and for the people in Melbourne can be got from Petro-ject 03 98737006.
The main high pressure pump is a Bosh one pt no 0580464070 and cost $140.

One last thing-You will need to unclip and turn the float around otherwise it will catch on the old/other outlet pipe. This is not difficult.

Why do you need a feeder pump?

Petrol- has a high vapour pressure (about 70 KPa at 37.8 degrees(RVP test method)) This means it doesnt siphon well if it is warm. Which it will be, after running the engine for a while. High vapour pressure also means gas bubbles in the fuel returning from the engine. This gas must be vented off some how. By passing the returning fuel back into the main tank your fuel vapour bubbles either vent out through the tank system or dissolve back into the bulk of the petrol.
High pressure rollervane EFI fuel pumps- Do deliver high pressure and high volume. However, have very poor suction and MUST be protected by a fine filter. I did try not using a filter on mine, and lasted about 45 minutes!. Unless they have a free flowing fuel supply these pumps will cavitate and make a very loud buzzing noise, easily audible over the engine. Even if they do manage to deliver fuel to the engine under these conditions they will not last too long.

So you are trying to suck a fluid (with poor suction characteristics) through a filter with a pump that doesnt suck well. You can see the problem.
The answer is to use an additional supply pump with reasonable suction and a high enough volume delivery to keep up with the main high pressure pump.

P.N. Sherman

Sorry to dis-agree, but I've been using a high pressure pump with no pre-filter on my V8 conversion for over 8 years without any problems......the SD1 Vitesse system had a filter after the return rail throughout production . It is vitally important to mount the pump at the same level as the feed pipe(mine's on a bracket just in front of the tank) so that the pump is gravity fed at all times. My filter is mounted on the N/S scuttle where it can be replaced annually.
M Barnfather

Maybe it's an Aussie thing, but my high press. pump lasted two days without a filter in the inlet line. Also check your tank first. My '71 rdstr had baffles already in the tank. I couldn't use the later sender/pickup because of them. I ended up sweating a pipe thru the original sender. Barrie E
Barrie Egerton

It's not an Aussie thing. My '74 fuel tank has baffles and the later sender from a '77 does not fit.
werner haussmann

Interesting to hear about the baffles. Neither my old or my two new tanks had these. I guess that if you are lucky enough to have a tank with baffles then you really don't need any sort of antisurge tank at all!
OT, if you can't make one for yourself, like Barrie, then there are hose fittings availiable to put a return line through/into the old sender. Go to a place that specializes in valves; a hydrolic hose place or somewhere that sells chemical plant bits and pieces etc. you want a right angled fitting with thin nuts and washers and seals both sides(of the tank sender). I work in a laboratory that samples gas (as in propane etc.. not as in American Petrol) and we have suitable fittings laying around all over the place.
P.N. Sherman

Right, pretty much sorted it all out through another forum.

I can keep the original tank and replace the sender with a later spec one - about £12.

I will used the outlet from the send to go to a low pressure pump via a low pressure filter.

The low pressure pump will feed a swirl pot, which then discharges to my nice spanky Bosch 910 motorsport fuel pump, then a high pressure filter, to the fuel rail.

The return from the fuel rail will be T-eed with the return from the swirl pot and plumbed into the original outlet from the tank.

Now, why not return to the fuel swirl pot from the fuel rail I hear you ask?!? Simple, many people I know have had fuel vapourisation problems with a set up like that.

The only problem is I need the low pressure pump to move the same or more amount of fuel than the bosch pump - easy - use a Holley blue pump.

All sorted! Just gotta go buy some bits now!
OT Hayter

I strongly advise you to put a filter between the swirlpot & the high press. pump. A filter costs peanuts compared to the cost of a High press. pump. Barrie E
Barrie Egerton

With you Barrie - you should see what was in my pre-filter when I last changed it.
RMW

OT if you use a large filter prior to the low pressure pump you won't need a swirl pot.
P.N. Sherman

This thread was discussed between 24/11/2006 and 29/11/2006

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